f(x) = 8 - 10x
g(x) = 5x + 4
Finding (fg)(-2).
First let us find fg(x), this is the same as f(g(x))
f(g(x))
f(5x + 4)
Recall, f(x) = 8 - 10x, therefore f(5x + 4) would be such that anywhere we see x in the f(x), we replace it with 5x + 4
f(x) = 8 - 10x
f(5x +4) = 8 - 10(5x + 4)
= 8 - 50x - 40
= -50x + 8 - 40
= -50x - 32
f(g(x)) = fg(x) = -50x - 32
fg(-2) = -50*(-2) - 32 = 100 - 32 = 68
Therefore fg(-2) = 68
I hope this helped.